1. Field of the Invention
This invention relates to a suitable technique for an ophthalmologic apparatus which automatically effects the position alignment of an eye to be examined and the pupil center of an eye examining portion to thereby effect eye examination and photographing.
2. Related Background Art
As a conventional ophthalmologic apparatus for effecting auto alignment, there is known one which projects a light beam from within the measurement optical axis of an eye examining portion to the cornea of an eye to be examined, detects the reflected light thereof by a light receiving element, detects the positional displacement between the eye to be examined and the eye examining portion on the basis of the detected reflected image, and drives the eye examining portion to thereby effect auto alignment.
Also, as disclosed in Japanese Patent Application Laid-open No. H09-066027, there is known an apparatus which detects the pupil center and effects auto alignment in vertical and left to right directions, and as disclosed in Japanese Patent Application Laid-open No. H09-131314, there is known an apparatus which effects alignment detection in a front to rear direction by the interval of the cornea reflected image of an anterior ocular illumination light source.
In the aforedescribed conventional examples, when they are applied, for example, to an objective type eye refractive power measuring apparatus in which it is required to effect measurement at the center of the pupil, alignment detection in vertical and left to right directions is effected at the center of the pupil and alignment detection in a front to rear direction is effected by separating the cornea reflected light beam of alignment light, as disclosed in Japanese Patent Application Laid-open No. H09-84760.
If in this case, an alignment light source and a measurement light source are used in common, the range within which the reflected light of alignment light from the cornea of an eye to be examined can be detected by a light receiving element will become narrow because the light beam of the measurement light source is thin.
Regarding the alignment detection in the front to rear direction, as disclosed in Japanese Patent Application Laid-open No. H09-131314, there is a detecting method using the interval of the cornea reflected image of anterior ocular illumination, but in this method, the interval of the corneal reflected image of the anterior ocular illumination is varied by the radius of curvature of the cornea.